Target has confirmed that hackers obtained customer debit card PINs (personal identification numbers) in the massive data breach suffered by the retailer during the busy holiday shopping season, but says customers should be safe, as the numbers were encrypted.

Some 40 million customer debit and credit cards were affected by the breach, but until now it wasn't clear that PINs were part of the hackers' massive haul.

"While we previously shared that encrypted data was obtained, this morning through additional forensics work we were able to confirm that strongly encrypted PIN data was removed," Target said in a statement on its website Friday. "We remain confident that PIN numbers are safe and secure. The PIN information was fully encrypted at the keypad, remained encrypted within our system, and remained encrypted when it was removed from our systems."

When Target customers use their debit cards, the PIN is secured with Triple DES encryption at the checkout keypads, according to the statement. "Target does not have access to nor does it store the encryption key within our system," it adds. "The PIN information is encrypted within Targets systems and can only be decrypted when it is received by our external, independent payment processor. What this means is that the 'key' necessary to decrypt that data has never existed within Targets system and could not have been taken during this incident."

The company didn't reveal how many PINs were taken, or whether it even knows the total at this point in its probe.

Target is still in the early stages of its investigation into the breach, according to Friday's statement. The company previously said it was working alongside the U.S. Secret Service and Department of Justice on the investigation.

U.S. lawmakers have called for an immediate investigation into Target's security practices. The retailer has said customers will not be forced to pay for any fraudulent charges on their card, and are also eligible to receive credit monitoring at no charge.